1. Field
Aspects of the present invention generally relate to an inkjet recording apparatus.
2. Description of the Related Art
When an inkjet recording apparatus has not discharged ink for a predetermined period, thickening of the ink in a nozzle of a recording head occurs, so that there is fear that the inkjet recording apparatus becomes unable to normally discharge the ink. To prevent such a problem, the inkjet recording apparatus performs a preliminary discharge operation, i.e., regularly discharges the ink in the nozzle during printing operation. The nozzle is thus maintained in a satisfactory condition.
However, if the inkjet recording apparatus performs the preliminary discharge operation at a position too close to an edge of a recording medium, there is fear that the preliminary-discharged ink adheres to and stains the recording medium. On the other hand, if the inkjet recording apparatus performs the preliminary discharge operation at a position far away from the recording medium, a moving distance of the recording head becomes long, so that throughput is lowered. As a result, it is necessary for the inkjet recording apparatus to perform the preliminary discharge operation at an appropriate position corresponding to a width of the recording medium.
U.S. Pat. No. 6,761,430 discusses a technique in which a carriage is provided with an optical sensor including a light emitting unit and a light receiving unit. The optical sensor then detects the recording medium based on an amount of light reflected from the recording medium, and identifies an edge position of the recording medium. The preliminary discharge operation is thus performed at the position based on the identified edge position.
The ink which is preliminary-discharged from the inkjet recording apparatus discussed in U.S. Pat. No. 6,761,430 is receptive to an absorbing member on a platen. However, if a large amount of ink is preliminary-discharged, the ink may not sufficiently dry on the absorbing member, and thus remain as a residual substance thereon. If the optical sensor then performs detection of the recording medium on the absorbing member in such a state, the following may occur. The light reflected from a surface of the ink residual substance may cause the optical sensor to falsely detect the recording medium even when there is no recording medium. The width of the recording medium may thus be misrecognized to be greater than the actual width. Further, if the carriage performs scanning while misrecognition has occurred, the carriage moves to an outer side of the recording medium when the preliminary discharge operation is to be performed.
Furthermore, the above-described inkjet recording apparatus conveys the recording medium using a conveyance roller pair and a discharge roller pair. When the inkjet recording apparatus conveys a center region of the recording medium, the recording medium is pinched by both the conveyance roller pair and the discharge roller pair. However, when the inkjet recording apparatus conveys a leading edge region or a trailing edge region of the recording medium, the recording medium is pinched by only one of the conveyance roller pair and the discharge roller pair. As a result, there is fear that the inkjet recording apparatus may convey the leading edge region or the trailing edge region of the recording medium while the recording medium is floating above the platen.
If the carriage moves to the outer side of the recording medium while the recording medium is floating, the carriage and the recording medium may interfere when the carriage performs scanning after reversing. In such a case, the recording medium may become rolled in, or a discharge port surface of the recording head may become damaged. As a result, if there is a possibility that the recording medium may float when the inkjet recording apparatus is to perform the printing operation and the preliminary discharge operation, the inkjet recording apparatus is required to scan the carriage without moving the carriage to the outer side of the recording medium.